VIDEO: Michelle Trachtenberg Finds Herself Under Fire on NCIS: LA

Gossip Girl alum Michelle Trachtenberg guest-stars on this week's Christmas-themed episode of NCIS: Los Angeles, and she has the marks to show for it."This is definitely the most action-packed role [I've done]. There was definitely more gunfire than I'm used ...

"This is definitely the most action-packed role [I've done]. There was definitely more gunfire than I'm used to," the actress tells TVGuide.com. "There were several - of course fake - weapons aimed in my direction, and there were car explosions and tons of stunts and special effects. I definitely picked up my fair share of bruises. Every time I tried to do something and then would get all bruised up they were like, 'Okay, let's go to the stunt girl,' and I'm like, 'Sounds good!' ... It was pretty intense."

Her character, Lily Lockhart, is the daughter of a senator who finds herself the victim of a home invasion on Tuesday's episode (9/8c, CBS). Callen (Chris O'Donnell) and Sam (LL Cool J) are sent in to find out whether the incident was random, or whether Lily was the intended target.

"The senator who has made some things come to pass that have created a lot of enemies for him, and people are trying to use his daughter to sort of threaten him," Trachtenberg explains. "Throughout the episode, we go on a wild, crazy save the damsel in distress mission."

Trachtenberg says she had been taking some time off from acting in order to focus on writing screenplays, but couldn't turn down the opportunity to work with one of her heroes, LL Cool J.

"I'm such a huge fan of his. I'm from Brooklyn, and ... he was absolutely amazing, one of my most favorite people that I've ever worked with," she says. "There was a part where I was running and got yanked too hard and fell and ripped up my hands and bruised up my body, and I was bleeding. He stood by me until the medic came over and disinfected it. He was like, 'Make sure you put on Neosporin.' So he was very caring."